Cannulated screws have been used for internal fracture fixation, and a single screw placement through the femoral neck has become the preferred treatment for fractures through the physeal plate. Fractures through the physeal plate are more commonly referred to as Slipped Capital Femoral Epiphysis.
Generally, such a fixation device comprises a hollow shaft having a predetermined cross-section and provided with threaded sections beginning at the medial end of the device spanning a predetermined length of the shaft. The fixation device is placed parallel to the neck of the femur and secures the fracture with compressive force applied by the spherical lateral screw head at the lateral cortex. The prior art typically describes a variety of screw systems comprising different shaft diameters, shaft lengths, thread pitches and thread lengths in order to offer a fixation device for all possible locations and extents of the fracture sites. The general configuration of cannulated screws is well illustrated in U.S. Pat. No. 7,207,994. Such described screws are non self-adjustable in length and, therefore incapable of providing a surgical fixation to stabilize fractured bones during the healing process without disrupting the normal bone growth particularly in pediatric patients.
In another example described in U.S. Published Patent Application No. 20070260248, an adjustable feature is incorporated into the screw allowing extension of the shaft length along a predetermined range. The screw has an outer member and an inner member connected together by a spring-like component. Once the shaft length is selected and the device is stabilized in said position, the device is inserted into the prepared canal of the femoral neck to fixate the bone segments, just as previously described for cannulated screws, in order to promote healing.
Other prior art include an intramedullary nail described as an adjustable solution for long bone fixation in U.S. Pat. No. 6,524,313. However, no prior art device has shown adjustable screw solutions for this regard. Therefore, there is a need in the art for an extendable screw system for surgical fixation of femoral neck fractures in pediatric patients.
Given the present design of cannulated screws used for the fixation of femoral neck fractures, including Slipped Capital Femoral Epiphysis, the compressive loads created by the medially threaded shafts and the lateral spherical screw heads inhibit the normal growth in young patients. Premature closure of the physeal plate is a reoccurring condition widely documented in the literature as a result of pinning and fixation via cannulated screws. Telescoping devices such as the Fassier-Duval Intramedullary Nail, whose fixation features do not thread into the physeal plate, have shown successful internal fixation of fractures and osteotomies in long bones without compromising the integrity of the physeal plate and thus allowing the continuation of normal patient growth.